Cooling fan with rotor blade flanges for controlling rotor movement

ABSTRACT

An exemplary cooling fan includes a housing having an air inlet and an air outlet opposite to the air inlet, a rotor received in the housing, and a stator received in the housing and rotatably supporting the rotor. The rotor includes a hub, blades extending outwardly from an outer periphery of the hub, and flanges slantwise extending from top edges of end portions of the blades. In operation of the cooling fan, air located at an outside of the cooling fan enters the air inlet and flows towards the blades and along the flanges thereby pressing the rotor towards a bottom of the stator along an axial direction of the cooling fan, and the air subsequently flows out of the cooling fan via the air outlet.

BACKGROUND

1. Technical Field

The disclosure generally relates to cooling fans such as those used in electronic devices, and particularly to a cooling fan having stable performance.

2. Description of Related Art

With continuing development of electronics technology, heat-generating electronic components such as CPUs (central processing units) are generating more and more heat when in operation. In typical electronic devices that employ CPUs, the heat requires immediate dissipation. Cooling fans are commonly used in combination with heat sinks for cooling the CPUs.

A typical cooling fan includes a fan housing forming a base at a central portion thereof, a stator mounted on the base, and a rotor rotatably supported by the stator. The stator includes a mounting portion formed at a central portion of the base, and a stator core mounted on the mounting portion. The stator core is made of steel. The rotor includes a hollow hub, a shaft mounted on the hub, and a magnet received in the hub. The shaft extends through the stator core. Magnetic interaction occurs between the stator core and the magnet, and drives the rotor to revolve around the stator core. Centrifugal force is generated when the rotor is rotating, and the centrifugal force acts on the rotor. The rotor is prone to move away from the stator under the centrifugal force. The amount of centrifugal force is changeable according to changes in the rotation speed of the rotor. Magnetic attraction between the stator core and the magnet tends to draw the rotor towards the stator along an axial direction of the fan. That is, the magnetic attraction force tends to counteract the centrifugal force. In general, the amount of magnetic attraction force is invariable. When the centrifugal force acting along the axial direction of cooling fan is equal to the magnetic attraction force, the rotor is in equilibrium and rotates steadily around the stator core of the stator. However, when the centrifugal force along the axial direction changes and is not equal to the magnetic attraction force, the rotor oscillates back and forth along the axial direction of the stator core of the stator.

What is needed, therefore, is an improved cooling fan which overcomes the above described shortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a cooling fan according to an exemplary embodiment of the present disclosure.

FIG. 2 is an isometric view of a hub of the cooling fan of FIG. 1.

DETAILED DESCRIPTION

An embodiment of a cooling fan in accordance with the present disclosure will now be described in detail below and with reference to the drawings.

Referring to FIG. 1, a cooling fan 100 of the present disclosure includes a fan housing 10, and a stator 20 and a rotor 30 received in the fan housing 10.

Referring also to FIG. 2, the rotor 30 includes a cylindrical hub 32, a shaft 34, a magnet 36 and a plurality of blades 38. The hub 32 includes a top wall 322, and a cylindrical sidewall 324 extending downwardly from a circumferential edge of the top wall 322. A seat 323 is formed in a central portion of the top wall 322. The shaft 34 extends downwardly from within the seat 323 to below the seat 323. The shaft 34 has a bottom free end 342. The blades 38 extend obliquely outwardly from an outer periphery of the sidewall 324 of the hub 32. The blades 38 are spaced from each other. The magnet 36 is annular and received in the hub 32. An outer periphery of the magnet 36 contacts an inner surface of the sidewall 324.

Each blade 38 is straight and includes a connecting section 381 extending from the hub 32, and an extending section 383 extending from the connecting section 381. The connecting section 381 is in the form of a tapering sheet. The connecting sections 381 extend obliquely along a counterclockwise direction of the outer periphery of the sidewall 324 of the hub 32, as viewed in FIG. 2. A transverse width (i.e. height) of the connecting section 381 generally increases from an inner end connected to the hub 32 to an outer end away from the hub 32. The extending section 383 is in the form of a rectangular sheet, and extends outwardly from the outer end of the connecting section 381. A length of the connecting section 381 along a longitudinal direction of the blade 38 is larger than a length of the extending section 383 along the longitudinal direction. The transverse width of the outer end of the connecting section 381 is slightly less than that of the extending section 383. Two slopes are respectively formed at a top end and a bottom end of the blade 38 at joints of the extending section 383 and the connecting section 381.

A flange 385 is formed on the top end of the extending section 383 to increase a contacting area of the blade 38. The flange 385 is an elongated sheet and slantwise extends from the top end of the extending section 383. An outer end of the flange 385 is coplanar with an outer end of the extending section 383. A length of the flange 385 along the longitudinal direction is less than that of the extending section 383. A transverse width of the flange 385 is less than that of the extending section 383. The flanges 385 of the blades 38 are arranged along the counterclockwise direction, as viewed in FIG. 2.

The stator 20 includes a stator core 22, a plurality of stator coils 24, a printed circuit board (PCB) 26, and an insulating frame 28. In FIG. 2, the stator coils 24 are schematically shown as four landscape-oriented boxes, each of which is crossed. The insulating frame 28 covers top and bottom sides of the stator core 22. The stator coils 24 are wound on the insulating frame 28 and around the stator core 22. Thus, the stator coils 24 are electrically separated from the stator core 22 by the insulating frame 28. The PCB 26 is attached to a bottom side of the insulating frame 28 and electrically connected with the stator coils 24 to control an electrical current flowing through the stator coils 24. A through hole (not labeled) is defined in a central portion of each of the stator core 22, the insulating frame 28 and the PCB 26. The through holes of the stator core 22, the insulating frame 28 and the PCB 26 are aligned and cooperatively define a mounting hole 27.

Referring back to FIG. 1, the fan housing 10 includes a hollow casing 12, a base 14 arranged at a central portion of the casing 12, and a plurality of ribs connecting the base 14 to the casing 12. The fan housing 10 defines an air inlet 17 at a top side thereof and an opposite air outlet 18 at a bottom side thereof. The base 14 is located at a center of the air outlet 18. A central tube 15 extends upwardly from a central portion of the base 14 towards the air inlet 17, for mounting the stator 20 thereon. The central tube 15 is hollow, defining a receiving hole 150 therein. A pair of bearings 80 are received in the receiving hole 150 of the central tube 15. In FIG. 2, the bearings 80 are schematically shown as four portrait-oriented boxes, each of which is crossed.

In assembly of the cooling fan 100, the central tube 15 is extended through the PCB 26, the insulating frame 28 and stator core 22 in series, with the stator 20 being pressed downwardly around the central tube 15. Thus the central tube 15 is received in the mounting hole 27. The hub 32 is covered over the stator 20, with the free end 342 of the shaft 34 passing through the middle of the bearings 80. The flanges 385 are located at the top side of the housing 10 adjacent to the air inlet 17.

When the cooling fan 100 is used, the rotor 30 rotates about the stator 20. Air between the blades 38 flows out from the cooling fan 100 via the air outlet 18. Air located at an outside of the cooling fan 100 enters the air inlet 17 and flows towards the top ends of the blades 38 and the flanges 385. The air flows along the flanges 385 and thereby tends to press the rotor 30 down towards a bottom of the stator 20 along an axial direction of the cooling fan 100, and such air subsequently flows out of the cooling fan 100 via the air outlet 18.

Because the flanges 385 are provided at the top ends of the extending sections 383, contact areas for the air to act on the blades 38 are increased. Thus, a pressing component force applied by the airflow on the blades 38 along the axial direction of the cooling fan 100 is increased. Accordingly, any oscillation of the rotor 30 along the axial direction of cooling fan 100 associated with an imbalance between centrifugal forces and magnetic attraction forces may be decreased or even eliminated altogether. As a result, stable and reliable performance of the cooling fan 100 is improved. Furthermore, because the flanges 385 extend slantwise from the top ends of the extending sections 383, the flanges 385 do not significantly obstruct airflow passing from the air inlet 17 to the air outlet 18.

It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

What is claimed is:
 1. A cooling fan comprising: a housing having an air inlet and an air outlet opposite to the air inlet; a rotor received in the housing and comprising a hub, a plurality of blades extending outwardly from an outer periphery of the hub, and a plurality of flanges slantwise extending from top edges of end portions of the blades; and a stator received in the housing and rotatably supporting the rotor; wherein in operation of the cooling fan, air located at an outside of the cooling fan enters the air inlet and flows towards the blades and along the flanges thereby pressing the rotor towards a bottom of the stator along an axial direction of the cooling fan, and the air subsequently flows out of the cooling fan via the air outlet.
 2. The cooling fan of claim 1, wherein the flanges are arranged along a counterclockwise direction.
 3. The cooling fan of claim 1, wherein each blade comprises a connecting section extending from the hub and an extending section extending from the connecting section, and the flange slantwise extends from a top end of the extending section.
 4. The cooling fan of claim 3, wherein each connecting section is in the form of a tapering sheet.
 5. The cooling fan of claim 4, wherein the blade is straight.
 6. The cooling fan of claim 4, wherein a transverse width of the connecting section generally increases from an inner end connected to the hub to an outer end away from the hub.
 7. The cooling fan of claim 6, wherein the extending section is in the form of a rectangular sheet and extends from the outer end of the connecting section.
 8. The cooling fan of claim 3, wherein a length of the connecting section along a longitudinal direction of the blade is larger than that of the extending section along the longitudinal direction.
 9. The cooling fan of claim 3, wherein the flange is an elongated sheet and slantwise extends from the top end of the extending section and oriented towards the air inlet of the housing.
 10. The cooling fan of claim 9, wherein an outer end of the flange is coplanar with an outer end of the extending section.
 11. The cooling fan of claim 10, wherein a length of the flange along the longitudinal direction is less than that of the extending section.
 12. The cooling fan of claim 1, wherein the blades radially extend from the hub and are spaced from each other.
 13. A cooling fan comprising: a rotor comprising a hub, a plurality of blades extending outwardly from an outer periphery of the hub, and a plurality of flanges slantwise extending from top edges of end portions of the blades; and a stator rotatably supporting the rotor; wherein in operation of the cooling fan, the flanges of the blades provide resistance to airflow arriving from above the cooling fan thereby pressing the rotor towards a bottom of the stator along an axial direction of the cooling fan while still allowing the airflow to pass out beyond bottoms of the blades.
 14. The cooling fan of claim 13, wherein the flanges are arranged along a counterclockwise direction.
 15. The cooling fan of claim 13, wherein the flange is an elongated sheet and slantwise extends from a top end of the blade.
 16. The cooling fan of claim 13, wherein each blade comprises a connecting section extending from the hub and an extending section extending from the connecting section, and the flange slantwise from the extending section.
 17. The cooling fan of claim 16, wherein each connecting section is in a form of a tapering sheet.
 18. The cooling fan of claim 18, wherein the connecting sections extend obliquely along a counterclockwise direction.
 19. The cooling fan of claim 17, wherein a transverse width of the connecting section generally increases from an inner end connected to the hub to an outer end away from the hub.
 20. The cooling fan of claim 17, wherein the extending section is in a form of a rectangular sheet and extends outwardly from the outer end of the connecting section. 